This invention relates to materials useful in the treatment of siliceous surfaces. More particularly it relates to compounds, aqueous solutions and compositions which are useful in imparting durable hydrophilicity to siliceous surfaces.
Although various types of materials have been suggested for use in imparting hydrophilicity to various substrates, all of such previously suggested materials have been less than desirable for one reason or another. For example, some of the earliest suggested materials for such use were common anionic or non-ionic surfactants (e.g., triethanolammonium oleate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, polyoxyalkylene sorbitol). These surfactants have been described for use in either solid or aqueous solution form. However, the major disadvantage associated with the use of such common surfactants is that the hydrophilicity and antifogging properties imparted by such materials simply do not exhibit very good durability during use, (i.e., such materials are easily dissolved by water and removed from the surface). Consequently, in order for such materials to be effective they must be reapplied to the surface at frequent intervals.
Another type of surfactant which has been described for use in imparting hydrophilic properties is a terpolymer of dimethyl silicone, polyethylene oxide, and polypropylene oxide. This type of surfactant, which is described, for example, in U.S. Pat. No. 3,337,351, suffers from the same drawbacks as discussed above, namely easy dissolution by water.
Still another type of surface active agent is described in U.S. Pat. No. 3,187,033. This type of material contains S--C bonded sulfo groups and displays physical and chemical properties similar to soaps. Thus, for example, these materials exhibit substantial surface tension lowering capabilities.
U.S. Pat. No. 3,507,897 describes siloxane surface active agents in aqueous media. These solutions preferably have a pH of from 5 to 8 so that the agents do not degrade. Additionally, these agents are said to exhibit excellent surface tension lowering capabilities.
U.S. Pat. No. 3,328,449 describes sulfopropylated, organofunctional silane and siloxane materials which are useful as detergents, ion exchange resins, wetting agents, anti-stat agents and polymerization catalysts for siloxanes. It is said that these materials may be provided in solution form and that suitable solvents include water. However, it is also said that such solvents must not react with the solute. There is no discussion therein of stable aqueous solutions of sulfonato-organosilanols or of siliceous surfaces rendered hydrophilic by treatment therewith.
U.S. Pat. No. 3,455,877 describes organosilicon epoxides wherein the epoxy group (or the radical containing the epoxy group) is attached to silicon by a Si--C linkage. These materials are said to be useful as emulsifiers, plasticizers, lubricants, etc. They are also said to be useful in preparing hydroxy sodium sulfonates by reacting the epoxides with sodium sulfite. There is no discussion of the preparation of stable aqueous solutions of such compounds or of the durably hydrophilic surfaces produced by contacting such compositions with siliceous surfaces.
The present invention provides compounds, aqueous solutions and compositions which are useful for imparting durable hydrophilicity to siliceous surfaces as well as the durably hydrophilic surfaces themselves. The hydrophilic treatments of the present invention are particularly useful where easy grease and wax removal is desired or required. Thus, for example, the treatments are useful on glass surfaces such as household windows, automobile windshields and windows, eyeglasses, and bathroom mirrors; glazed ceramic surfaces such as ceramic tile and ceramic bathroom fixtures; and silicon oxide treated polymeric and non-polymeric surfaces.
Siliceous surfaces treated in accordance with the present invention are not rendered grease or wax repellent (i.e., they are not made oleophobic). Consequently, greases and waxes may attach to the treated surfaces. However, the treated surfaces are rendered readily cleanable so that grease and wax may be removed therefrom by simple water rinsing alone although very light rubbing may also be helpful in some instances.
Because the present invention imparts durable hydrophilicity to siliceous surfaces, such surfaces may be readily cleaned even after having been repeatedly previously soiled or marked by grease or wax and then cleaned. Moreover, surfaces treated in accordance with the present invention are substantially easier to clean than are surfaces which have not been so treated.
Examples of greases and waxes which have been found to be readily removable from surfaces treated in accordance with the present invention are butter, margarine, lard, natural sebum (skin oil), artificial sebum, motor oils, motor greases, paraffin wax and wax pencil marks. Still other substances such as elastomeric-based adhesives, pressure-sensitive adhesives, thermoplastic (solvent soluble) adhesives, thermosetting adhesives, epoxy adhesives, silicon based adhesives, etc. are readily removed from these surfaces.
Preferably the sulfonato-organosilanol compounds are provided in aqueous solutions. Surprisingly, such solutions are stable over long periods of time even at relatively high concentrations of the sulfonato-organosilanol compounds (e.g., 10% to 15% by weight). Thus, the treatment activity of the solutions is retained and no precipitate is formed therein upon prolonged storage. Moreover, such solutions may be provided at various concentrations of the sulfonato-organosilanol compounds. Consequently, the solutions may be provided in a concentrated form for storage or shipping that may be later diluted for use.
Additionally the preferred aqueous solutions provide thin, durable antifogging coatings on siliceous surfaces. Thus individual water droplets will not form and remain on surfaces treated with said solutions (i.e., said surfaces do not fog over) despite repeated exposures to conditions of high humidity.
Surprisingly the foregoing results are achieved even though the sulfonato-organosilanol compounds do not exhibit typical surfactant characteristics. Thus these compounds do not significantly affect the surface tension of aqueous media.